1. Field of the Invention
The invention relates to a ring-mark printing device for identifying electrical cables. When ring marks are to be painted on the circular surface of an electrical cable, the operation is preferably carried out under non-contact conditions. The electrical cables painted with ring marks are usually employed in the automobile industry, and the ring marks serve to distinguish the quality and/or size of such cables.
2. Description of Background Information
Known ring-mark printing devices usually employ either a printing system in which ink is ejected through ink nozzles under pressure and painted on a cable surface, or a system in which a marking drum is provided with a tubular surface having ink nozzles, through which ink is ejected by the centrifugal force exerted by drum rotation.
An example of the former (first) printing system is disclosed in a Japanese utility model application published under No. SHO 61-60413, and an example of the latter (second) system is disclosed in a Japanese utility model application published under No. HEI 7-25517.
FIG. 1 shows process steps performed by the second printing system, in which an electrical cable is manufactured and then painted with ring-like marks. In this system, a conductor wire 2 is continuously supplied from a supply reel 1 along a predetermined path. The conductor wire 2 is then passed through an extruding machine 3 and coated while being extruded, thereby yielding a coated electrical cable 4. The coated electrical cable 4 is guided into a printer machine 5, in which the cable is painted with ring-like marks used for cable identification. The marked electrical cable 4 is cooled in a cooling bath 6, withdrawn through a withdrawal unit 7, and reeled continuously around a receiving reel 8.
FIGS. 2, 3 and 4 illustrate the following device units: a printer box 10, in which the electrical cable 4 is subjected to a printing operation; a pair of marking drums 11 and 12 mounted in the printer box 10, the two marking drums being arranged sequentially along the cable""s feed axis, and in staggered positions and at some distance relative to the feed axis; a driving mechanism for rotating both marking drums 11 and 12 (not shown in the figures); an ink tank 13 for storing marking ink; an ink-supply mechanism for feeding ink from the ink tank 13 to inside the marking drums 11 and 12 through a supply pipe 14; and an ink return pipe 15 for forwarding the ink contained in the printer box 10 to the ink tank 13.
As shown in FIGS. 5 and 6, the marking drums 11 and 12 respectively include a plurality of ink-jet nozzles (six nozzles in the illustrated example) arranged at a given interval in the circumferential direction of the tubular surface. The ink 16 stored in the marking drum 11 is ejected through each ink-jet nozzle, by virtue of the centrifugal force generated by the rotating drum, so that each half side face of the electrical cable 4, when advancing along the feed axis P, is painted with ejected ink.
FIGS. 3 to 7 show the marking process in detail. When the electrical cable 4 advances along the feed axis P of the cable and passes in front of a first marking drum 11, a first semicircular side face of the cable 4 is painted with ink 16 ejected from the marking drum 11 placed upstream, and is printed with a semicircular mark 17a (FIG. 5). Likewise, when the electrical cable 4 advances further and passes in front of a second marking drum 12 placed downstream, a second semicircular side face of the cable 4 is painted with ink 16 ejected from the marking drum 12, and is printed with a semicircular mark 17b (FIG. 6). In this manner, the outer circular face of the electrical cable 4 can be printed with complete ring marks 17 (or band marks) at a given interval.
In order to match the position of the first semicircular mark 17a with that of the second semicircular mark 17b, the marking drums 11 and 12 are driven in synchronization.
In such a centrifugal printing system, equipment is designed with the presumption that the ink 16 continues to be ejected correctly. Accordingly, when electrical cables 4 with and without ring marks are produced in the same production line, either the printer device 5 is cut off, or a special ink-shield is installed for deviating ejected ink 16 from the electrical cable 4.
Thus, when the centrifugal printing system is applied, the printer device 5 may optionally be turned off when the electrical cables are to be processed without printing. However, this switching off process involves a certain time lag before the rotational speed of the marking drums 11 and 12 can be lowered to a point where the ink 16 stops jetting out. As a result, the portion of electrical cables 4 processed during the switching off time must be cast aside as a substandard product. Conversely, when the marking drums 11 and 12 are again put into motion, it takes a while to regain full rotational speed and stability. The portion of electrical cables 4 produced during this period must also be cast aside as a substandard product. Those substandard products formed during the restarting period may reach several kilometers of the electrical cable 4, which is cast aside as a length loss.
When the marking drums 11 and 12 are immobile for a long time (the standstill duration limit being several minutes to some fifteen minute), ink 16 solidifies inside the ink-jet nozzles. The disassembling and cleaning of the nozzles will thus become necessary when the marking drums are to be started.
When a special ink shield is used, it must be replaced during a replacement standstill. Such a standstill incurs of course the production of substandard electrical cables, resulting in a length loss of several hundred meters. Moreover, ink 16 may be spattered around from the marking drums 11 and 12 while the shield is replaced, and may smear peripheral equipment. As the ink 16 contains organic solvents, the working environments are also deteriorated.
Moreover, when the shield is replaced, it may inadvertently thrust the electrical cable 4, and cut it off.
In order to reduce such accidents, prior art solutions usually opted for preparing different production schedules, depending on whether electrical cables 4 are printed with ring marks or not. However, such production methods are not well suited to small-lot production and suffer from a low running rate of the production line.
In order to solve the above-noted problems, the present invention provides a ring-mark printing device for identifying electrical cables, which reduces the length loss of the electrical cables, improves the running rate of the production line of the cables, and is suited to small-lot production.
To this end, there is provided a ring-mark printing device for identifying electrical cables. The device includes a printer box having a feed axis and configured to pass an electrical cable along the feed axis and a pair of marking drums with a respective outer circular face. The marking drums are contained in the printer box and arranged in staggered positions along the feed axis and at a given distance away therefrom. Further, the marking drums include ink-jet nozzles at the outer circular face. Further yet, the marking drums are respectively adapted to contain ink and eject the ink through the ink-jet nozzles by virtue of centrifugal forces exerted by drum rotation, in order to print the ring-mark around the circular surface of the electrical cable.
According to the present invention, the printer box is provided with an ink shield including substantially concentrically positioned outer and inner tubular bodies which are configured to surround the electrical cable from a given distance. The outer tubular body further includes at least one outer ink-orifice at a position facing one of the marking drums and the inner tubular body includes at least one inner ink orifice.
The inner tubular body is then mounted such that it can slide through the outer tubular body along the feed axis in a freely movable way, and such that the inner ink-orifices can be joined with a corresponding outer ink-orifices to be ready for ring-mark printing, or moved away from a corresponding outer ink-orifice to be prevented from ring-mark printing.
Preferably, the outer tubular body is divided into three outer tubular segments by two outer ink-orifices, and the outer tubular segments are held by a shield support.
Further, the shield support may have an opening in a portion adjacent to the outer ink-orifices.
Suitably, the inner tubular body is divided into three inner tubular segments by two inner ink-orifices, and the inner tubular segments are connected to each other by a linking element.
More suitably, the outer and inner tubular bodies include a corresponding outer and inner longitudinal slit along a diametrically lowermost portion over the length of the corresponding body. The outer and inner longitudinal slits thus communicate with corresponding outer and inner ink-orifices. The outer and inner longitudinal slits communicate with each other and have a space sufficiently large for allowing the electrical cable to pass, such that the ink shield can be fitted into the printer box from the top thereof in a freely engageable and removable way.
The inner longitudinal slit may include first and second longitudinal rims, which are divided into corresponding first and second rim segments by the inner ink-orifices. In this arrangement, the first rim segments are placed farther, relative to one of the marking drums, than the second rim segments. The linking element is then mounted between two adjacent first rim segments.
Preferably, the inner tubular body includes at least one stop, such that, when the inner tubular body is slid through the outer tubular body, the at least one stop can determine one of a position ready for ring-mark printing and a position for impeding the ring-mark printing.
More preferably, the inner tubular body is longer than the outer tubular body, so that two end portions of the inner tubular body extend outwardly from two end portions of the outer tubular body along the feed axis, and the two end portions of the inner tubular body respectively carry first and second stops, such that the inner tubular body can determine a position ready for ring-mark printing and a position for impeding the ring-mark printing, by sliding the inner tubular body until one of the first and second stops abuts against the outer tubular body.